1. Field of the Invention
The present invention pertains to techniques for controlling the operation of multi-stage processes. More particularly, the present invention relates to methods and apparatus for operating batch processing systems, including a plurality of process stations for sequentially receiving goods arranged in batches. The present invention finds particular application to continuous batch washing systems which maintain the isolation of batches of goods to be laundered with individual process requirements.
2. Description of Prior Art
Continuous batch, multi-stage processing systems are known, and may be operated by means of programmed controls. In particular, continuous batch washing systems may include a plurality of washing modules mutually aligned and arranged to sequentially receive a stream of goods to be laundered, the goods being grouped in individual, mutually-isolated batches. The batches are passed from module to module, being maintained in each module for specified times and subjected therein to various stages in the laundering process.
U.S. patent application Ser. No. 59,272, filed July 19, 1979, issued Dec. 2, 1980 as U.S. Pat. No. 4,236,393, assigned to the present assignee, and which is incorporated herein by reference, discloses a continuous batch washing system including such an array of washing modules, known as a "tunnel". In the tunnel system of the '393 patent, all of the goods-handling drums of the various washing modules are mechanically linked so that agitation is effected in all of the modules in unison. Also, each module includes a scoop, as part of the drum, by which the goods in the module may be transferred to the next module in sequence by appropriate rotation of the drum. Thus, with all module drums rotating to transfer their respective loads in unison, batches may be transferred from one module to the next throughout the array of modules at the same time. Selected additives, including water, steam, soap and bleach, for example, may be appropriately added to individual modules to accommodate the laundering requirements of the specific batches of goods contained in the respective modules. Each batch is thus processed according to its requirements as the batch proceeds through the array of modules. The tunnel system may be operated by a transferable program system wherein process programmed controls assigned to individual batches may be advanced with the batches from module to module, and used to directly operate the modules containing the instant batches.
A modular tunnel processing system is potentially a highly efficient means for operating on a continuous stream of batches of goods. For example, in the aforementioned tunnel system, as many batches as there are modules in the system may be processed simultaneously. As one batch completes its transition through the module array, another batch may be added to the first module at the beginning of the process. Thus, as long as additional batches of goods to be processed are available, the tunnel system may be operated continuously. However, to maximize such efficiency of operation, and to reduce the hands-on requirements of the operator, automatic operations of the system may be maximized. As the details of the various process steps must be modified to meet changing needs of the batches, or to "fine tune" the batch processing, the control system must be sufficiently flexible to accommodate on-site process operation program changes.